2006/06/04 by Keivan G. Stassun, M. van den Berg, Eric Feigelson +1 · 5 citations
Physics and Astronomy · Social Sciences · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Educational Leadership and Practices #astro-ph
paper · pdf · doi:10.1086/506422
published as Astrophys.J.649:914-926,2006 · 69 pages, 46 figures, accepted by ApJ
arxiv created 2006/06/04 · openalex publication_date 2006/09/27 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We present a database of BVRI time-series photometry of the Orion Nebula Cluster obtained with two ground-based telescopes at different longitudes to provide simultaneous coverage with the 13 day Chandra observation of the cluster. The resulting database of simultaneous optical and X-ray light curves for some 800 pre-main-sequence (PMS) stars represents, by a factor of hundreds, the largest synoptic, multi-wavelength-regime, time-series study of young stars to date. This database will permit detailed analyses of the relationship between optical and X-ray variability among a statistically significant ensemble of PMS stars, with the goal of elucidating the origins of PMS X-ray production. In this first paper, we present the optical observations, describe the combined X-ray/optical database, and perform an analysis of time-correlated variability in the optical and X-ray light curves. We identify 40 stars (representing 5% of our study sample) with possible time-correlated optical and X-ray variability. Examples of both positive and negative time correlations are found, possibly representing X-ray flares and persistent coronal features associated with both cool and hot surface spots (i.e., magnetically active regions and accretion shocks). We also find two possible examples of "white-light" flares coincident with X-ray flares; these may correspond to the impulsive heating phase in solar-analog flares. However, although interesting, these represent unusual cases. More generally, we find very little evidence to suggest a direct causal link between the sources of optical and X-ray variability in PMS stars. The conclusion that accretion is a primary driver of X-ray production in PMS stars is not supported by our findings.